Arc furnaces for producing steel are provided with a device which makes it possible to tilt the furnace vessel to empty the melt into a casting vessel, e.g., a steel casting ladle, and to tap slag.
Designs in which the furnace vessel is seated in a vessel frame, which lies on at least two tilting cradles, have been known, on the one hand. During the tilting of the furnace, the toothed tilting cradle, which is usually of a circular design, rolls on a horizontal, likewise toothed substructure.
In another prior-art design, corresponding to the design according to FIG. 1, the tilting cradle of the furnace is designed to be such that it is mounted on rollers and is tilted by a drive mechanism into the tapping position as well as into the slag-tapping position.
A device for tilting electric arc furnaces, in which the electrodes do not follow the tilting movement, has been known from German Auslegeschrift No. DE-AS 1,084,445. The tilting of the furnace vessel with a discharge spout is achieved by means of a rolling path, which is displaceable during tilting and on which the rolling cradle rolls.
The rolling cradle has laterally arranged guide rails, which come into contact with the rollers during the movement of the cart located under the rolling cradle out of its normal position.
The right-hand guide rail comes into contact with the right-hand roller during the tilting of the vessel for tapping the molten steel, as a result of which it brings about the tilting of the vessel in a defined area around the upper fulcrum point.
Tilting into a fulcrum, which is located in the vicinity of the center of gravity of the furnace vessel, will then take place during the further movement of the cart/rolling path to the right. The guide rail now moves farther along the right-hand roller, but on the straight section of the guide rail.
The cart under the rolling cradle has both a carrying function and a moving function. The bilaterally mounted rollers have no carrying function, but are used for guiding only.
The disadvantage of the principle applied as the first state of the art is the fact that the center of the furnace is displaced there on the horizontal substructure corresponding to the tilting geometry and the rolling behavior of the tilting cradles, and it migrates either in the direction of the tapping side or in the direction of the slag-tapping side, depending on the tilting movement of the furnace vessel. There is a distance between the center of the furnace and the center of the tilting cradle, which is determined, in terms of design, by the value of the tapping weight.
One disadvantage of the second state of the art is the fact that during tilting, the bottom tapping device arranged in the vessel frame is displaced in the direction of the center of the furnace during the emptying of the steel from the furnace vessel. The consequence of this is that the steel casting ladle, which is located in a steel-removing cart, must move in the direction of the center of the furnace during tapping, corresponding to the tilting movements of the arc furnace. This means that the cart and the ladle must be moved farther under the furnace, especially when the furnace vessel must be completely emptied and no bottom residue may remain in the furnace vessel.
One disadvantage of the latter state of the art is the fact that the electrodes must be pulled out of the vessel for tilting the vessel, even over only a small tilting range.
Even though this tilting device makes it possible to completely empty the furnace vessel, the design is very complicated, because one or two displaceable carts/rolling paths with hydraulic drive is necessary, and with a widely protruding support structure are required for the travel path of the cart, which cannot be used for a d.c. arc furnace with supply devices arranged on the lower part of the vessel for a bottom electrode.
The travel path of the steel-removing cart with the steel casting ladle has limitations in terms of design in a d.c. arc furnace, because the devices for power supply and the cooling devices for the bottom electrode are installed under the bottom of the furnace vessel. In addition, these devices must be protected from the radiant heat of the molten steel in the steel casting ladle.
The prior-art tilting device according to the first state of the art also cannot be used when the arc furnace is to be supplied with preheated scrap iron continuously through an opening in the side wall in the area of the center of tilting via a stationary, covered chute and when the hot flue gases are to be drawn off at the same time through the cover of the chute to preheat the scrap iron to be charged in.